Tunnel-kiln and method of operating same



I. DH. DRESSLER. TUNNEL KILN AND METHOD 0F OPERATING SAME.

APPLICATION FILED FEB. 26, 1920.

Patented Feb. 22, 1921.

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UNITED STATES PATENT OFFICE.

PHILIP DH. DRESSLER, ZANESVILLE, OHIO, ASSIGNOR TO AMERICAN DRESSLER TUNNEL KILNS, INC., OF NEW-YORK, N. Y., A CORPORATION OF NEW YORK.

TUNNEL-KEN AND METHOD OF OPERATING SAME.

Spercication of Letters Patent. Patented Feb. 22, 1921.

Application led February 26, 1920. VSerial No. 361,554.

Vmanufacture of clay products and Vin annealing glass and metals, and for other purposes. The general object of the invention is to provide a simple and eitective method of, and apparatus for overcoming the tendency for the ends of such a. kiln to become too hot.

' y The various features of novelty which 20.

characterize my invention are pointed out with particularity in the claims annexed to and forming a part oi' this specification. For a better understanding oi' this invention however, its advantages and the objects attained with its use, reference should be had to the accompanying drawings and descriptive matter in which I have illustrated vand described in some detail embodiments of my invention.

Of the drawings; Figure 1 is a plan view in section of a `tunnel kiln.

well knownk Dressler tunnel kilnV type and comprises an inclosed chamber A in which is located a track B for goods carrying cars E which enter the kiln at one end and leave at the opposite end. entrance; end of the chamber A is normally closedby av door F, and the exit end by a door G, though one or both of these doors may sometimes be omitted. At each side of the pathway for the goods or wares of the cars .VE are combustion chambers C. The latter have ilue passages D in their walls whereby a transverse convection current circulation As shown thek lines indicated by the arrows in Fig. 4. The. combustion chambers C do not extend to either end of the chamber A. At one end each combustion chamber C is connected to the. adjacent ends ot a group of tubes H which extend iii alinement with the combustion chamber to the eXit end A2 of the chamberl A, and are there connected to a header H which receives atmospheric air through the inlet H2. The opposite end ot each combustion chamber C is connected to tubes I which form a longitudinal extension ot the combustion chamber and are connected at their ends remote from the latter to a header I. Each header I is provided with an outlet J connected to a stack J. Combustible gas is Vsupplied to each combustion chamber C at the end of the latter to which the pipes II are connected as by means of a gas supply pipe K.

In the normal intended operation oi the kiln shown in the drawings, the air suppliedto the combustion chambers through the pipes I-I, and the gas supplied through the inlets I unite in combustion in the coinbustion chambers and the burning gases and products oi' combustion tlow through the combustion chambers and pipes K to the stack J. The goods entering the chamber A at A are progressively heated up as they move through the preheatingq zone containing the pipes I and the high temperature zone containing the combustion chambers C and are then cooled down` as they move through the cooling zone ot the chamber in which thel pipes II are located. The cooling oi the goods causes the air in the pipes H to be raised to a hic-h temperature desirable for maintaining eiiicient combustion in the combustion chambers C. In so tar as above de` scribed the kiln illustrated presents nothing now novel with me. i

In the use of a tunnel kiln, whether of the muiile tyoe such as that shown by way oi example in the accompanying drawings, or

'- ot the open tired type, difficulty is fre- Vtoo hot at its top. I have found .that this diiiiculty can be successfully overcome, or avoided by suitably injecting cold air into the entrance end of the kiln along the roof of the kiln chamber. I believe that the tendency to overheating at the top of the entrance end of a tunnel kiln is due to a convection current circulation of the kiln atmosphere, upward in the hotter central air along the bottoni of the kiln, and that the desirable result which l obtain by a suitable injection of cool air into the end of the kiln is due to a modification by the injected air of the convection current circulation referred to.

ln the apparatus shown in the drawings the air injected into the top of the entrance end A of the kiln is supplied by a blower L connected to a metal duct or delivery trunk M located in the kiln chamber ad jacent they roof of the latter and terminating in a discharge mouth M. The latter is shaped to deliver a fiat wide horizontal stream of air directed away from the entrance end of the kiln along the roof of the kilnchamber. ln operation l believe this stream engages the oppositely flowing convection current stream of the kiln atmosphere approaching the entrance end of the kiln with the result that both streams are deflected downward to the bottom of the kiln. At the bottom of the kiln part of the downwardly deflected air turns and flows along` the bottom of the kiln chamber back toward the center of the kiln and part :Hows toward therentrance end of the kiln where it passes out into the atmosphere through cracks about the door or leakage ports especially provided for the purpose. The circulation just described is indicated by the arrows applied to Fig. 2. ln' a kiln of the particular type disclosed wherein there is no forced flow ofthe kiln atmosphere which masks or materially modifies the convection current tendency of the kiln atmosphere, the exit end of the kiln has the Vsame tendency as the entrance end to become too hot at the top, and this tendency may be overcome in the same way at each end of the kiln. l, therefore, provide at the exit end of the kiln a blower LA and delivery duct MAV constructed and operatingl like the blower L and duct M. lWith the blowers L and LA at the opposite ends of the tunnel it is possible to put the main interior of the kiln under a pressure slightly above that of the atmosphere without creating objectionable currents in the kiln atmosphere. This increase of pressure is desirable in some cases. lt insures that any leakage through the walls of the combustion chambers shall be from the kiln chamber into the combustion chambers and not in the opposite direction. The effect ofthe discharges through the ducts M and MA, and the changes in the circulation of the l kiln atmosphere made thereby is to appreciably reduce the temperature at theends of the kiln particularly at the top and to equalize the temperatures at different levels in the end of the kiln and to some extent in the body of the kiln chamber. The reduction in the kiln and end temperatures thus obtained is Vveryidesirable in handling some kinds of wares and in some cases permits of a shorter kiln than would otherwise be required. rlhe changes in the circulation of the kiln atmosphere in the body portion of the kiln chamber produced by the blowers L and LA make it somewhat easier to keep up the desirable high temperature there. lt will be understood, of course, that the air discharged by the ducts M and MA must be adjusted, as by giving the blowers L and LA the proper speed, to arrest the opposing convectioncurrents at the proper points in the kiln chamber and in particular must not be powerful enough to materially modify the normal convectional circulation in the central portion'of the kiln chamber. lt is obvious, of course, that where the kiln atmosphere is not composed of air but of some other gaseous substance, such substance may be blown into the kiln through the ducts lill and MA.

.While in accordance with the provisions of the statutes, l have illustrated and described the best embodiments of my invention now known to me, it will be apparent to thoseskilledvin the art that changes may be made in the form of my invention as set forth in the appended claims without departing from its spirit, and in particular it is to be understood that in some cases and particularly with certain type of kilns it may be desirable to maintain a cold air barrier at one end only of the kiln chamber.

Having, now described my invention, what l claim as new and desire to secure by Letters Patent, is:

l. rEhe method of operating a tunnel kiln which consists in nniintaining,1 an atmosphere formed by a hot body of gaseous material in a central portion of the kiln chamber without substantial movement of said atmosphere encept for convection current circulation thereof, and blowing gaseous material into the end of the kiln along the top of the kiln chamber so as to create a downward flow of the kiln atmosphere between the end and center of the kiln with a resubstance into the entrance end of the kiln in fa stream directed toward the opposite end of the chamber and flowing along the top of the latter.

3. In a continuous tunnel kiln the combination with the kiln chamber and mulle heating provisions therefor, of means for blowing a gaseous substance into one end of the kiln chamber in a stream directed to- Ward the opposite end of the kiln chamber and flowing along the top of the latter.

4. In a continuous tunnel kiln, the combination With the kiln chamber and mufle heating provisions therein, or" means for maintaining the pressure of the atmosphere of the kiln chamber above that of the external atmosphere.

5. In a continuous tunnel kiln the combination with the kiln chamber and means for heating it, of means for blowing a gaseous substance into each end of the kiln cham-v ber in a stream directed toward the opposite end of the kiln chamber and iowing along the roof of the latter.

Signed at Columbus in the county of Franklin and State of Ohio this 18th day of Feb. A. D. 1920.

PHILIP DH. DRESSLER. 

